Output shaft rotation restriction structure of hand-held machine tool

ABSTRACT

A output shaft rotation restriction structure of a hand-held machine tool having a shell, a drive shaft in the shell, and an output shaft in the shell, perpendicular to the drive shaft, provided with a grinding piece, and in linkage with the drive shaft via a steering gear set; two sides of the hand-held machine tool may be defined according to an extension line of the drive shaft. The output shaft rotation restriction structure includes a mounting hole on the shell, specifically, one of the two sides of the hand-held machine tool, a restriction hole on the output shaft and facing the mounting hole, and a rotation restriction group including a holder in the mounting hole, a restriction plug on the holder, and a spring, the restriction plug being forced into the restriction hole to interfere with the rotation of the output shaft.

FIELD OF THE INVENTION

The invention relates to an output shaft rotation restriction structure, in particular to an output shaft rotation restriction structure of a hand-held machine tool.

BACKGROUND OF THE INVENTION

To avoid that an output shaft is driven by a grinding piece when replacement of the grinding piece for a conventional hand-held machine tool, so as to allow the grinding piece to be removed relative to the output shaft difficultly. In the process of replacing the grinding piece by using two wrenches in the prior art, the output shaft is fixed by any one of the two wrenches and the other one of the two wrenches rotates a sleeve at a bottom end of the output shaft, thereby releasing the sleeve and replacing the grinding piece. However, a conventional method using two wrenches is rather inconvenient; as a result, manufacturers of the hand-held machine tool alternatively provided a rotation restriction structure for the output shaft on the hand-held machine tool to overcome this defect.

In the case of Taiwan Patent No. 1288684, which provides an output shaft rotation restriction structure to restrict the rotation of a steering gear set and further restrict the rotation of the output shaft. The output shaft is difficult to be fixed once the steering gear set falling off from an engagement with the output shaft.

In addition, in the cases of China utility model patent no. 206464951U, Taiwan utility model patent no. M449058U and China publication No. 108972342, an output shaft rotation restriction structure of a hand-held machine tool restrict the rotation of the output shaft directly, but the output shaft rotation restriction structure is provided in an extension direction of a drive shaft. Taking Taiwan utility model patent no. M449058U as an example, the output shaft rotation restriction structure is located above a head part of the hand-held machine tool, however, a drive switch of the hand-held machine tool and the output shaft rotation restriction structure are both located on a plane which is in an extension direction of the drive shaft, as shown in FIG. 3. Further, when a user intends to replace a grinding sheet of the hand-held machine tool, the user holds the hand-held machine tool with a single hand and put a thumb on the output shaft rotation restriction structure, so that the user operates the output shaft rotation restriction structure with the thumb to fix the output shaft. However, the user is likely to put the other four fingers on a drive switch, hence the possibility of mistakenly touching the drive switch when operating the output shaft rotation restriction structure.

SUMMARY OF THE INVENTION

It's a main object of the invention to solve the problem that a user is likely to touch a drive switch by mistake when operating a conventional output shaft rotation restriction structure by one hand.

To achieve the above object, the invention provides an output shaft rotation restriction structure of a hand-held machine tool. The hand-held machine tool comprises a shell, a drive assembly disposed in the shell, a drive shaft disposed in the shell and driven by the drive assembly, and an output shaft disposed in the shell and perpendicular to the drive shaft in an extension direction thereof, wherein the output shaft is provided with a grinding piece, connected to the drive shaft via a steering gear set, and driven by the drive shaft, and wherein two sides of the hand-held machine tool is defined on the basis of an extension line of the drive shaft. The output shaft rotation restriction structure includes a mounting hole, a restriction hole, and a rotation restriction group. The mounting hole is provided on the shell and positioned on one of the two sides of the hand-held machine tool. The restriction hole is provided on the output shaft and facing the mounting hole. And the rotation restriction group includes a holder disposed in the mounting hole, a restriction plug disposed on the holder and exposed outside the shell, and a spring disposed in the holder and provides the restriction plug with a restoring force, wherein the restriction plug is inserted into the restriction hole to restrict the rotation of the output shaft when the restriction plug is forced to move towards the output shaft.

In an embodiment, the restriction hole extends through the output shaft.

In an embodiment, the restriction hole is deviated from a center of the output shaft.

In an embodiment, the holder includes a first opening for the restriction plug to insert in and a second opening, coaxial with the first opening, for the restriction plug to extend out.

In an embodiment, the restriction plug includes an operation part exposed outside the shell, a connection part extending from the operation part and disposed in the holder, and a restriction part extending from the connection part and extending out of the second opening, wherein the connection part includes a convex rib abutting against a periphery of the first opening to prevent the restriction plug falling off from the holder.

In an embodiment, a size of the restriction part is smaller than a size of the connection part.

In an embodiment, the connection part includes a stage difference connection surface adjacent to the restriction part, and a guide inclined surface connecting the stage difference connection surface and extending in an opposite direction from the restriction part.

In an embodiment, one side of the convex rib facing the restriction part is connected to the guide inclined surface without stage difference.

In an embodiment, the holder is a tubular structure.

In an embodiment, the holder includes a first thread provided on an outer surface of the holder, and the mounting hole includes a second thread fitting the first thread.

In an embodiment, the holder includes a first portion inserted into the shell and a second portion exposed outside the shell, and the first thread is disposed on the first portion.

In an embodiment, a cross-section of the holder at the second portion is polygonal.

The invention has the following advantages compared with the prior art according to the foregoing embodiments: the output shaft rotation restriction structure is selectively provided on one of the two sides of the hand-held machine tool, and the extension plane of the output shaft rotation restriction structure intersects with the extension plane of the drive switch of the hand-held machine tool. As a result, if a user intends to replace the grinding piece, he needs to change his holding posture that places his thumb on the output shaft rotation restriction structure and his other four fingers not placed on the drive switch, thereby avoiding the situation that the drive switch is touched by mistake. In addition, the rotation restriction structure for the output shaft directly restricts the output shaft instead of interfering with the output shaft through other elements indirectly. Thus the situation that the rotation of the output shaft cannot be specifically restricted due to disengagement among structures can be avoided. Furthermore, the rotation restriction group is an independent component. Namely, the hand-held machine tool only needs to form the mounting hole and the restriction hole during the assembling process and the rotation restriction group as an independent component can be directly assembled in the mounting hole so as to finalize assembling of the hand-held machine tool which is easier than the prior art and featuring convenience in assembling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic perspective view of an embodiment of the invention.

FIG. 2 shows a schematic perspective view of an embodiment of the invention.

FIG. 3 shows a first schematic cross-sectional view of an embodiment of the invention.

FIG. 4 shows a second schematic cross-sectional view of an embodiment of the invention.

FIG. 5 shows a third schematic cross-sectional view of an embodiment of the invention.

FIG. 6 is a schematic diagram of an operation of an embodiment of the invention.

FIG. 7 shows a schematic enlarged cross-sectional view of some elements of the invention.

FIG. 8 is a schematic diagram of the mounting hole on one side of the hand-held machine tool held for use in an embodiment of the invention.

FIG. 9 is a schematic diagram of the mounting hole on the other side of the hand-held machine tool held for use in an embodiment of the invention.

FIG. 10 shows a schematic cross-sectional view of another embodiment of the invention.

FIG. 11 is a schematic diagram of an operation of another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The details and technical content of the invention will now be described with reference to the drawings as follows.

Refer to FIG. 1, FIG. 2, FIG. 3 and FIG. 4, the invention provides an output shaft rotation restriction structure 11 of a hand-held machine tool 10. Before describing the output shaft rotation restriction structure 11, the hand-held machine tool 10 is described first. In different embodiments, the hand-held machine tool 10 is a grinding machine tool including a grinding piece 20, or a cutting machine tool including the grinding piece 20, wherein the grinding piece 20 shown in FIG. 1 is provided only for explanation and is not limited thereto. Further, the hand-held machine tool 10 not only includes the output shaft rotation restriction structure 11, but also includes a shell 14, a drive assembly 15, a drive shaft 16, and an output shaft 17. The shell 14 includes a grip part 141 and a head part 142 connected to the grip part 141. In detail, the head part 142 is connected to one end of the grip part 141, the grip part 141 is provided for a user to grip, and the grip part 141 forms a basic appearance of the hand-held machine tool 10. In one embodiment, the head part 142 is connected to one end of the grip part 141 and the head part 142 is perpendicular to the grip part 141. Further, the drive assembly 15 is disposed within the grip part 141 and is controlled to be actuated, wherein the drive assembly 15 may be a motor (not shown) and an impeller (not shown). The drive shaft 16 is located within the grip part 141, and one end of the drive shaft 16 is connect with the drive assembly 15 so that the drive shaft 16 is driven when the drive assembly 15 is actuated, which also drives other elements within the hand-held machine tool 10 simultaneously. Furthermore, the output shaft 17 is disposed in the head part 142 of the shell 14, and the output shaft 17 is perpendicularly disposed with respect to the drive shaft 16. Specifically, the output shaft 17 includes an extension line 171 which is perpendicular to an extension line 161 of the drive shaft 16. Further, the output shaft 17 is not directly connected to the drive shaft 16, but is connected to the drive shaft 16 via a steering gear set 18. The output shaft 17 is driven by the drive shaft 16 through the steering gear set 18. In an embodiment, the steering gear set 18 includes a first steering gear 181 located at one end of the drive shaft 16 facing the output shaft 17 and a second steering gear 182 located at one end of the output shaft 17 facing the drive shaft 16. The first steering gear 181 is driven by the drive shaft 16; and the second steering gear 182 is driven by the output shaft 17. The first steering gear 181 and the second steering gear 182 are perpendicularly disposed so that the first steering gear 181 is partially engaged with the second steering gear 182. After the first steering gear 181 is driven by the drive shaft 16, the first steering gear 181 drives the second steering gear 182 to further drive the output shaft 17. Also, when the output shaft 17 is provided with the grinding piece 20, the output shaft 17 is driven by the steering gear set 18 to drive the grinding piece 20 to rotate.

Also, referring to FIG. 2, FIG. 3 and FIG. 4, two sides 101, 102 of the hand-held machine tool 10 is defined on the basis of the extension line 161 of the drive shaft 16 when observed from a top view angle, and the output shaft rotation restriction structure 11 is provided at one of the two sides 101, 102 of the hand-held machine tool 10. Further, the aforementioned top view angle is an angle at which a person directly looks down where the hand-held machine tool 10 is placed with the grinding piece 20 underneath. Further, the output shaft rotation restriction structure 11 is provided on the output shaft 17. In an embodiment, an extension direction 133 of the output shaft rotation restriction structure 11 intersects with an extension line 171 of the output shaft 17 at 90 degrees, as shown in FIG. 5. In more detail, the output shaft rotation restriction structure 11 includes a mounting hole 111, a restriction hole 112 and a rotation restriction group 113. The mounting hole 111 is provided on the shell 14 and positioned on one of the two sides 101, 102 of the hand-held machine tool 10 where is above a center line of the head part 142. The center line described herein is an intermediate position between one side of the head part 142 provided with an opening 144 and the other side which is opposite the opening 144.

With reference to FIG. 3, FIG. 4, and FIG. 5, the restriction hole 112 is provided on the output shaft 17, and the restriction hole 112 and the mounting hole 111 are located at the same height. The restriction hole 112 rotates with the output shaft 17 when the output shaft 17 is driven. Accordingly, the restriction hole 112 forms two states that facing the mounting hole 111 and not facing the mounting hole 111 during rotation. Further, the restriction hole 112 does not necessarily face the mounting hole 111 after the output shaft 17 stops rotating, and thus the restriction hole 112 is allowed to face the mounting hole 111 by rotating the output shaft 17 or the like. Further, in the embodiment, the restriction hole 112 is actually in a groove shape, that is, the restriction hole 112 in this embodiment does not penetrate through the output shaft 17. Further, in an embodiment, the restriction hole 112 is deviated from the center of the output shaft 17 to be disposed.

Further, the rotation restriction group 113 is disposed in the mounting hole 111, and the rotation restriction group 113 includes a holder 114, a restriction plug 115 and a spring 116. The holder 114 is disposed in the mounting hole 111 to provide the restriction plug 115 being disposed, and the restriction plug 115 is inserted into the holder 114. One end of the restriction plug 115 is exposed outside the shell 14; and the other end of the restriction plug 115 is protruded out of the holder 114 or to be stowed in the holder 114. And further, the spring 116 is disposed in the holder 114 and sleeved on the restriction plug 115, and two ends of the spring 116 respectively abut against the holder 114 and the restriction plug 115.

With reference to FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6, one embodiment of the output shaft rotation restriction structure 11 will now be described. First, it is assumed that the restriction hole 112 has directly faced the mounting hole 111, and the rotation restriction group 113 has not been operated. If the restriction plug 115 is pressed, the restriction plug 115 presses the spring 116 to allow the spring 116 including a restoring force, and at the same time, the restriction plug 115 is forced to move towards a direction facing the output shaft 17, so that one end of the restriction plug 115 facing the restriction hole 112 inserts into the restriction hole 112, thereby restricting the rotation of the output shaft 17. Once the restriction plug 115 is no longer to be pressed, the spring 116 will release the restoring force and push the restriction plug 115 to return, so that the restriction plug 115 moves towards a direction which is opposite the output shaft 17, at the time that the output shaft 17 is free to rotate without being interfered by the restriction plug 115.

With reference to FIG. 1, FIG. 4, FIG. 8, and FIG. 9, if the user intends to replace the grinding piece 20, the user needs to change his holding posture, placing the thumb on the output shaft rotation restriction structure 11, for operating the hand-held machine tool 10. Further, the output shaft rotation restriction structure 11 is selectively arranged on one of the two sides 101, 102 of the hand-held machine tool 10 viewed from the top view angle so as to match up the user's dominant hand for holding the hand-held machine tool 10 upon replacing the grinding piece 20. For example, if the mounting hole 111 is positioned at the right side of the extension line 161, that is, the side 101 of the hand-held machine tool 10, the hand-held machine tool 10 is used by a left-handed user, and the rotation restriction group 113 is operated by left thumb of the user, as shown in FIG. 8. On the contrary, if the mounting hole 111 is positioned at the left side of the extension line 161, that is, the side 102 of the hand-held machine tool 10, the hand-held machine tool 10 is used by a right-handed user, and the rotation restriction group 113 is operated by right thumb of the user, as shown in FIG. 9. As a continued description, after the user operates the rotation restriction group 113 to fix the output shaft 17, a wrench 30 clamps a groove 172 of the output shaft 17 to fix the wrench 30. After rotating the wrench 30, a sleeve 173 at the end of the output shaft 17 is unscrewed, thereby removing the grinding piece 20 to be replaced. After this, the user inserts a connection shaft 21 of the grinding piece 20 to be mounted into an opening 174 of the sleeve 173, and screw tight the sleeve 173 to engage the grinding piece 20 with the output shaft 17. It should be noted that the grinding piece 20 of the invention may also be directly secured on the output shaft 17, i.e., the method of engaging the grinding piece 20 with the output shaft 17 as described hereinabove, and is not limited thereto.

Further, the output shaft rotation restriction structure 11 is disposed at one of the two sides 101, 102 of the hand-held machine tool 10, and an extension plane of the output shaft rotation restriction structure 11 intersects with an extension plane of a drive switch 143 of the hand-held machine tool 10. As a result, if the user changes his holding posture to put a thumb on the output shaft rotation restriction structure 11 for replacing the grinding piece 20, the other four fingers of a hand will not put on the drive switch 143, and accordingly reducing a situation that the user mistakenly touches the drive switch 143 when operating the output shaft rotation restriction structure 11 to replace the grinding piece 20. Further, the rotation restriction group 113 directly restricts the output shaft 17 instead of interfering with the output shaft 17 through other elements indirectly. Compared with the invention, a situation may be happened in the prior art that the output shaft 17 cannot be really restricted once other elements fall off from the output shaft 17. Further, the hand-held machine tool 10 is formed with the mounting hole 111 and the restriction hole 112 during the assembling process of the invention, and the rotation restriction group 113 is an independent component to be directly assembled in the mounting hole 111 so as to finalize assembling which is easier than the prior art.

Referring to FIG. 1, FIG. 2 and FIG. 3, in an embodiment, the head part 142 is formed with an opening 144 in an opposite direction from the grip part 141, and the opening 144 allows the output shaft 17 to be inserted into the head part 142. Further, the output shaft 17 includes an engagement section 175, a connection section 176 connected with one end of the engagement section 175, and a restriction section 177 connected with the connection section 176 and relative to the other end of the engagement section 175. The engagement section 175 extends into the opening 144 and is assembled with the head part 142, and the engagement section 175 is stowed in the head part 142 after finalizing assembling. The connection section 176 is connected with one side of the engagement section 175 without facing the head part 142 and extends towards a side which is opposite the head part 142; and one side of the connection section 176 without facing the engagement section 175 is provided to engage the restriction section 177. One end of the restriction section 177 without facing the connection section 176, and one end of the engagement section 175 without facing the connection section 176 together define a length of the output shaft 17. Further, the restriction section 177 is provided for engaging the grinding piece 20 and the sleeve 173. In detail, the restriction section 177 is assembled with the grinding piece 20 first and then assembled with the sleeve 173 to limit an engagement position of the grinding piece 20. In an embodiment, the output shaft 17 includes a third thread 178 which is disposed next to the restriction section 177, the sleeve 173 includes a fourth thread 179 fitting the third thread 178, and the third thread 178 is engaged with the fourth thread 179 to allow the sleeve 173 to be secured on the output shaft 17.

In another aspect, referring to FIG. 3 and FIG. 4, the hand-held machine tool 10 further includes a bearing group 19 engaged with the output shaft 17 to assist the output shaft 17 in rotating. In an embodiment, the bearing group 19 includes a first bearing 191 and a second bearing 192, wherein the first bearing 191 is connected with a side of the engagement section 175 facing the head part 142, i.e., the first bearing 191 is located above the center line of the head part 142. Further, the second bearing 192 is connected with a side of the engagement section 175 facing the connection section 176, i.e., the second bearing 192 is located below the center line of the head part 142.

In another aspect, referring to FIG. 4, FIG. 5 and FIG. 7, in an embodiment, the holder 114 is a tubular structure, and the holder 114 includes a first opening 117 and a second opening 118. The first opening 117 is provided on a side of the holder 114 which is opposite the mounting hole 111, and the first opening 117 is provided for the restriction plug 115 to insert in. The second opening 118 is coaxial with the first opening 117, and the second opening 118 is provided for the restriction plug 115 to extend out upon being forced. In another embodiment, the holder 114 is engaged with the mounting hole 111. The holder 114 includes a first thread 119 provided on an outer surface of the holder 114, the mounting hole 111 includes a second thread 120 fitting the first thread 119, and the holder 114 is secured in the mounting hole 111 by screwing the first thread 119 of the holder 114 on the second thread 120 of the mounting hole 111. Further, after the holder 114 is engaged with the mounting hole 111, the holder 114 includes a first portion 121 inserted into the shell 14, and a second portion 122 exposed outside the shell 14. The first portion 121 is provided with the first thread 119, the first portion 121 is shaped to fit the mounting hole 111 to allow the restriction plug 115 to be inserted therein, and the first portion 121 is configured as a hollow cylinder. Further, the second portion 122 is provided on a side of the first portion 121 without facing the output shaft 17. In an embodiment, a cross-section of the holder 114 at the second portion 122 is polygonal. Further, in an embodiment, the holder 114 includes a restriction rib 132 disposed on the second portion 122 to prevent the holder 114 from mating with the mounting hole 111, thereby limiting an engagement position of the holder 114 and the mounting hole 111.

In another aspect, the restriction plug 115 includes an operation part 123, a connection part 124 and a restriction part 125. The operation part 123 is exposed outside the shell 14 after the rotation restriction group 113 is engaged in the mounting hole 111. The connection part 124 extends from the operation part 123 in a direction facing the output shaft 17, and the connection part 124 is disposed in the holder 114 after finalizing the engagement. In an embodiment, a size of the operation part 123 is larger than a size of the connection part 124, thereby allowing the user to press the operation part 123 conveniently when operating the restriction plug 115. Further, the restriction part 125 extends from the connection part 124 in a direction which is opposite the operation part 123, the restriction part 125 is normally disposed in the holder 114, and the restriction part 125 extends out of the holder 114 to interfere with the restriction hole 112 when the restriction plug 115 is forced. In an embodiment, a size of the restriction part 125 is smaller than a size of the connection part 124.

As a continued description, referring to FIG. 4, FIG. 5 and FIG. 7, in order to prevent the restriction plug 115 falling off from the holder 114, the connection part 124 includes a convex rib 126 abutting against a periphery of the first opening 117. In particular, the convex rib 126 is disposed on a side of the connection part 124 facing the restriction part 125. The convex rib 126 abuts against the first opening 117 when the restriction plug 115 is pushed by the spring 116 without being forced, thereby preventing the restriction plug 115 from falling off. Further, the connection part 124 includes a stage difference connection surface 127 which is adjacent to the restriction part 125, and a guide inclined surface 128 connected with the stage difference connection surface 127 and the convex rib 126. The guide inclined surface 128 is disposed on the stage difference connection surface 127 which extends in an opposite direction from the restriction part 125. The guide inclined surface 128 assists the restriction plug 115 in displacing along the guide inclined surface 128 when the restriction plug 115 is engaged with the holder 114. In an embodiment, a side of the convex rib 126 facing the restriction part 125 is connected to the guide inclined surface 128 without stage difference. Specifically, after the guide inclined surface 128 assists in inserting the restriction plug 115 into the holder 114, the other side of the convex rib 126 facing the guide inclined surface 128 forms a stopper to prevent the restriction plug 115 falling off from the holder 114. Further, in an embodiment, the holder 114 is formed with a receiving groove 129 facing the restriction plug 115, the rotation restriction group 113 includes a sealing ring 130 disposed in the receiving groove 129, the sealing ring 130 is in contact with the restriction plug 115, and the sealing ring 130 and the restriction plug 115 together restrict a lubricating oil covered on the steering gear set 18 to flow into the holder 114.

Referring to FIG. 2, FIG. 9, FIG. 10 and FIG. 11, in an embodiment, in order to allow the output shaft 17 to be more stably restricted by the output shaft rotation restriction structure 11, the restriction hole 112 is a through hole 131. That is, the restriction hole 112 extends through the output shaft 17. When implementing this embodiment, the rotation restriction group 113 also allows the restriction plug 115 not interfering with the rotation of the output shaft 17 upon not being forced, as shown in FIG. 10. Further, if the rotation restriction group 113 is forced, the restriction plug 115 is forced to move towards the output shaft 17, and the restriction plug 115 extends into the through hole 131 to interfere with the rotation of the output shaft 17, as shown in FIG. 11. 

What is claimed is:
 1. An output shaft rotation restriction structure of a hand-held machine tool, the hand-held machine tool comprising a shell, a drive assembly disposed in the shell, a drive shaft disposed in the shell and driven by the drive assembly, and an output shaft disposed in the shell and perpendicular to the drive shaft in an extension direction thereof, wherein the output shaft is provided with a grinding piece, connected to the drive shaft via a steering gear set, and driven by the drive shaft, and wherein two sides of the hand-held machine tool is defined on the basis of an extension line of the drive shaft; the output shaft rotation restriction structure comprising: a mounting hole provided on the shell and positioned on one of the two sides of the hand-held machine tool, a restriction hole provided on the output shaft and facing the mounting hole, and a rotation restriction group including a holder disposed in the mounting hole, a restriction plug disposed on the holder and exposed outside the shell, and a spring disposed in the holder and provides the restriction plug with a restoring force, wherein the restriction plug is inserted into the restriction hole to restrict rotation of the output shaft when the restriction plug is forced to move towards the output shaft.
 2. The output shaft rotation restriction structure of the hand-held machine tool according to claim 1, wherein the restriction hole extends through the output shaft.
 3. The output shaft rotation restriction structure of the hand-held machine tool according to claim 1, wherein the restriction hole is deviated from a center of the output shaft.
 4. The output shaft rotation restriction structure of the hand-held machine tool according to claim 3, wherein the holder includes a first opening for the restriction plug to insert in and a second opening coaxial with the first opening for the restriction plug to extend out.
 5. The output shaft rotation restriction structure of the hand-held machine tool according to claim 4, wherein the restriction plug includes an operation part exposed outside the shell, a connection part extending from the operation part and disposed in the holder, and a restriction part extending from the connection part and extending out of the second opening, wherein the connection part includes a convex rib abutting against a periphery of the first opening to prevent the restriction plug falling off from the holder.
 6. The output shaft rotation restriction structure of the hand-held machine tool according to claim 5, wherein a size of the restriction part is smaller than a size of the connection part.
 7. The output shaft rotation restriction structure of the hand-held machine tool according to claim 6, wherein the connection part includes a stage difference connection surface adjacent to the restriction part, and a guide inclined surface connecting the stage difference connection surface and extending in an opposite direction from the restriction part.
 8. The output shaft rotation restriction structure of the hand-held machine tool according to claim 7, wherein one side of the convex rib facing the restriction part is connected to the guide inclined surface without stage difference.
 9. The output shaft rotation restriction structure of the hand-held machine tool according to claim 4, wherein the holder is a tubular structure.
 10. The output shaft rotation restriction structure of the hand-held machine tool according to claim 9, wherein the holder includes a first thread provided on an outer surface of the holder, and the mounting hole includes a second thread fitting the first thread.
 11. The output shaft rotation restriction structure of the hand-held machine tool according to claim 10, wherein the holder includes a first portion inserted into the shell and a second portion exposed outside the shell, and the first thread is disposed on the first portion.
 12. The output shaft rotation restriction structure of the hand-held machine tool according to claim 11, wherein a cross-section of the holder at the second portion is polygonal. 